Visual perception and perceptual disorders
- Created by: Emily-Jade99
- Created on: 02-01-18 18:17
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- Visual perception and perceptual disorders
- Definition of perception
- Perception - The process by which we recognise what is represented by the information provided by our sense organs
- Perception is a rapid, automatic and unconscious process
- The visual system allows us to detect and interpret information from visible light in order to build a representation of our environment
- Human wavelength of visible light = 380-760 nanometeres
- The eye
- Light is refracted as it passes through the cornea
- Light then passes through the pupil (controlled by iris) and is further refracted by the lens
- Cornea and lens act together as a compound lens (projects inverted image onto retina)
- Retina consists of photoreceptor cells that contain 2 main opsins (protein molecules)...
- Rod opsins - Used to see at low levels of light
- Cone opsins - Used to distinguish colour at normal levels of light
- The visual system
- Optic nerve
- Information travels from eye to brain through the optic nerve
- Sends information to places like the thalamus and SCN
- Optic chiasm - Where the optic nerve from both eyes meet and cross (base of hypothalamus)
- Optic tract - Information travels from right visual field in left optic tract and vice versa (track terminates in lateral geniculate nucleus)
- Primary visual cortex receives information directly from LGN
- Optic nerve
- Perception of form
- Most of what we see can be classified as figure or background (depends on observer)
- Changes in brightness, colour or texture creates the perception of edges
- If edges form continuous boundaries, we perceive the space enclosed by the boundary as a figure
- Templates - Special patterns stored by the visual system
- When we perceive, the visual system searches through templates and compares them with the stimulus (allows us to retrieve information)
- Prototypes - Idealised patterns of a particular shape
- With prototypes, the visual system accepts a degree of disparity
- Feature detection models - Visual system encodes images of familiar patterns in terms of distinctive features
- Top-down processing (role of content) - We often don't recognise objects in isolation (context helps us recognise them)
- Often, top-down and bottom-up processes are used together in perception
- Perception of depth
- Binocular cues
- Convergence - Both eyes look at same point of scene
- Retinal disparity - The amount of disparity produced by images of an object on the 2 retinas provides an important clue abut its distance from us
- Binocular cues
- Definition of perception
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